Coating compositions, such as paints, that include latex polymer particles typically also include a coalescent (i.e., coalescing agent or film-forming agent) in addition to pigments and fillers. The coalescent functions as a solvent as well as a plasticizer for the polymer particles to soften the latex polymer particles and assist in the formation of a continuous coating or film after applying to a surface and allowing to dry.
Useful coalescents are generally stable in the presence of water, compatible with other ingredients typically used in paint formulations, particularly the latex polymers, such that the stability of the latex-based composition is not compromised. They are also typically sufficiently volatile to escape when the applied coating composition is allowed to dry, but sufficiently nonvolatile to evaporate more slowly than other ingredients (e.g., drying retarders, antifreezes) that delay film formation. However, there is a general desire in the industry to reduce volatile organic emissions, thereby reducing the environmental and health concerns.
Governments have established regulations setting forth guidelines relating to volatile organic compounds that may be released into the atmosphere. To reduce the level of volatile organic compounds, new high solids coating compositions have been developed as well as powder coating compositions that do not include volatile compounds, have a reduced concentration of volatile compounds, or incorporate compounds having a lower volatility. Reducing the volatility of coalescents, solvents, plasticizers, etc. can adversely affect the balance of properties needed in a latex-based coating composition, however. Thus, there is a need for coalescents, solvents, plasticizers, etc. that can be used in coating compositions, such as paints, that do not compromise stability, compatibility, film formation ability, or the desirable properties of the applied coating, etc.
The present invention provides a class of compounds that have a relatively low volatile organic content. Such compounds can be used in coating compositions, preferably paints, as coalescing agents, solvents, plasticizers, etc. A suitable coalescent is dispersible in the coating composition, which is preferably stable over time. Preferably, the compound, when used as a coalescent, facilitates the formation of polymer films of the latex polymer at a temperature of less than about 25xc2x0 C. (more preferably, at about 4xc2x0 C. to about 10xc2x0 C., and most preferably, at about 4xc2x0 C. to about 5xc2x0 C.). Thus, there is provided a coating composition that includes a latex polymer and a coalescent (which can also function as a solvent or a plasticizer). Such coating compositions can be coated onto a substrate and dried, as with a paint, for example.
In one embodiment, a coating composition (preferably, a paint) includes: a latex polymer; and a coalescent having the formula: R1xe2x80x94(C(O)xe2x80x94Xrxe2x80x94O)nxe2x80x94R2 wherein: R1 is an organic group (preferably, having less than 100 carbon atoms); X is a divalent organic group (preferably, having 2 to 8 carbon atoms, and more preferably, 3 to 5 carbon atoms); r is 0 to 1; n is 1 to 10 (preferably, n is 1 to 5, more preferably, n is 1 to 3, and most preferably, n is 2 to 3); and R2 is hydrogen or an organic group (preferably, having less than 100 carbon atoms); with the proviso that R1 includes at least three carbon atoms when X is not xe2x80x94(CH2)sxe2x80x94 wherein s is 2 to 8; with the proviso that the coalescent has less than two aliphatic unsaturated carbon-carbon bonds when r is zero (preferably, the coalescent does not include aliphatic unsaturated carbon-carbon bonds when r is zero, and more preferably, the coalescent does not include aliphatic unsaturated carbon-carbon bonds); wherein the coalescent has a volatile organic content of less than about 50% (preferably, less than about 30%, more preferably, less than about 20%, and most preferably, less than about 15%) and is dispersible in the coating composition. Preferably, r is one.
In another embodiment, a coating composition includes: a latex polymer; and a coalescent having the formula: R1xe2x80x94(C(O)xe2x80x94Xrxe2x80x94O)nxe2x80x94R2 wherein: R1 is an organic group; X is a divalent organic group; r is 0 to 1; n is 1 to 10; and R2 is hydrogen or an organic group; with the proviso that R1 includes at least three carbon atoms when X is not xe2x80x94(CH2)sxe2x80x94 wherein s is 2 to 8; with the proviso that the coalescent does not include aliphatic unsaturated carbon-carbon bonds; with the proviso that r is one when R2 is H; wherein the coalescent has a volatile organic content of less than about 50%, is dispersible in the coating composition, and facilitates the formation of polymer films of the latex polymer at a temperature of less than about 25xc2x0 C. (preferably, at a temperature of about 4xc2x0 C. to about 10xc2x0 C., and more preferably, at a temperature of about 4xc2x0 C. to about 5xc2x0 C.).
In another embodiment, a coating composition includes: a latex polymer; and a coalescent having the formula: R1xe2x80x94(C(O)xe2x80x94Xrxe2x80x94O)nxe2x80x94R2 wherein: R1 has the formula R3xe2x80x94(CH2)mxe2x80x94(O(CH2)p)qxe2x80x94 wherein R3 is an alkyl or aryl group, m is 0 to 24, p is 1 to 4, and q is 0 to 50; X has the formula xe2x80x94(CH2)sxe2x80x94, wherein s is 2 to 8; r is 0 to 1; n is 1 to 10; and R2 is hydrogen or R1; wherein the coalescent has a volatile organic content of less than about 50%, is dispersible in the coating composition, and facilitates the formation of polymer films of the latex polymer at a temperature of less than about 25xc2x0 C. (preferably, at a temperature of about 4xc2x0 C. to about 10xc2x0 C., and more preferably, at a temperature of about 4xc2x0 C. to about 5xc2x0 C.).
In yet another embodiment, a coating composition includes: a latex polymer; and a coalescent having the formula: R1xe2x80x94(C(O)xe2x80x94Xxe2x80x94O)nxe2x80x94H wherein: R1 is a hydrocarbyl moiety or an organic group containing substituents selected from the group of nonperoxidic oxygen atoms, hydroxyl groups, and combinations thereof; X is a divalent hydrocarbyl moiety or an organic group containing nonperoxidic oxygen atoms and carbonyl groups; and n is 1 to 10; wherein the coalescent has a volatile organic content of less than about 50% (preferably, less than about 30%) and is dispersible in the coating composition.
In still another embodiment, a coating composition includes: a latex polymer; and a coalescent having the formula: R1xe2x80x94(C(O)xe2x80x94Xxe2x80x94O)nxe2x80x94H wherein: R1 is a hydrocarbyl moiety or an organic group containing substituents selected from the group of nonperoxidic oxygen atoms, hydroxyl groups, and combinations thereof; X has the formula xe2x80x94(CH2)sxe2x80x94, wherein s is 2 to 8; and n is 1 to 10; wherein the coalescent has a volatile organic content of less than about 50% (preferably, less than about 30%) and is dispersible in the coating composition.
In another embodiment, a coating composition includes: a latex polymer; and a coalescent having the formula: R1xe2x80x94(C(O)xe2x80x94Xxe2x80x94O)nxe2x80x94H wherein: R1 is a hydrocarbyl moiety or an organic group containing nonperoxidic oxygens; X is an organic group containing nonperoxidic oxygens and carbonyl groups; and n is 1 to 10; wherein the coalescent has a volatile organic content of less than about 50% (preferably, less than about 30%) and is dispersible in the coating composition.
The present invention also provides methods of coating that include: providing a coating composition as described herein; applying the coating composition to a substrate (e.g., wall); and allowing the coating composition to dry.
The term xe2x80x9cdispersiblexe2x80x9d in the context of a dispersible coalescent means that the coalescent can be mixed into the coating composition to form a uniform mixture without the use of high shear mixing.
The term xe2x80x9cstablexe2x80x9d in the context of a coating composition containing a dispersible coalescent means that the coalescent does not phase separate from the coating composition upon standing at 120xc2x0 F. (49xc2x0 C.) for four weeks.
The terms xe2x80x9cvolatile organic contentxe2x80x9d and xe2x80x9cVOCxe2x80x9d herein mean the volatility of the compound as measured by ASTM method D2369-90.
The term xe2x80x9corganic groupxe2x80x9d means a hydrocarbon (i.e., hydrocarbyl) group with optional elements other than carbon and hydrogen in the chain, such as oxygen, nitrogen, sulfur, and silicon that is classified as an aliphatic group, cyclic group, or combination of aliphatic and cyclic groups (e.g., alkaryl and aralkyl groups). The term xe2x80x9caliphatic groupxe2x80x9d means a saturated or unsaturated linear or branched hydrocarbon group. This term is used to encompass alkyl, alkenyl, and alkynyl groups, for example. The term xe2x80x9calkyl groupxe2x80x9d means a saturated linear or branched hydrocarbon group including, for example, methyl, ethyl, isopropyl, t-butyl, heptyl, dodecyl, octadecyl, amyl, 2-ethylhexyl, and the like. The term xe2x80x9calkenyl groupxe2x80x9d means an unsaturated linear or branched hydrocarbon group with one or more carbon-carbon double bonds, such as a vinyl group. The term xe2x80x9calkynyl groupxe2x80x9d means an unsaturated linear or branched hydrocarbon group with one or more carbon-carbon triple bonds. The term xe2x80x9ccyclic groupxe2x80x9d means a closed ring hydrocarbon group that is classified as an alicyclic group, aromatic group, or heterocyclic group. The term xe2x80x9calicyclic groupxe2x80x9d means a cyclic hydrocarbon group having properties resembling those of aliphatic groups. The term xe2x80x9caromatic groupxe2x80x9d or xe2x80x9caryl groupxe2x80x9d means a mono- or polynuclear aromatic hydrocarbon group. The term xe2x80x9cheterocyclic groupxe2x80x9d means a closed ring hydrocarbon in which one or more of the atoms in the ring is an element other than carbon (e.g., nitrogen, oxygen, sulfur, etc.).
Substitution is anticipated on the organic groups of the coalescents used in the coating compositions of the present invention. As a means of simplifying the discussion and recitation of certain terminology used throughout this application, the terms xe2x80x9cgroupxe2x80x9d and xe2x80x9cmoietyxe2x80x9d are used to differentiate between chemical species that allow for substitution or that may be substituted and those that do not allow or may not be so substituted. Thus, when the term xe2x80x9cgroupxe2x80x9d is used to describe a chemical substituent, the described chemical material includes the unsubstituted group and that group with O, N, Si, or S atoms, for example, in the chain (as in an alkoxy group) as well as carbonyl groups or other conventional substitution. Where the term xe2x80x9cmoietyxe2x80x9d is used to describe a chemical compound or substituent, only an unsubstituted chemical material is intended to be included. For example, the phrase xe2x80x9calkyl groupxe2x80x9d is intended to include not only pure open chain saturated hydrocarbon alkyl substituents, such as methyl, ethyl, propyl, t-butyl, and the like, but also alkyl substituents bearing further substituents known in the art, such as hydroxy, alkoxy, alkylsulfonyl, halogen atoms, cyano, nitro, amino, carboxyl, etc. Thus, xe2x80x9calkyl groupxe2x80x9d includes ether groups, haloalkyls, nitroalkyls, carboxyalkyls, hydroxyalkyls, sulfoalkyls, etc. On the other hand, the phrase xe2x80x9calkyl moietyxe2x80x9d is limited to the inclusion of only pure open chain saturated hydrocarbon alkyl substituents, such as methyl, ethyl, propyl, t-butyl, and the like. The term xe2x80x9chydrocarbyl moietyxe2x80x9d refers to unsubstituted organic moieties containing only hydrogen and carbon.